The Spanish verb 'armar' comes from the Latin verb 'armare', meaning 'to arm' or 'to equip with weapons'. The Latin 'armare' itself was derived from the Latin noun 'arma', which meant 'weapons'. This etymology shows a straightforward development from the concept of weapons to the action of equipping someone with weapons, which has carried through to modern Spanish.

A closely related and simpler Spanish word is 'arma' (weapon), which comes directly from the same Latin root 'arma'. While 'armar' is the action of equipping or arming, 'arma' is the noun referring to the weapon itself. You might also encounter 'armado' (armed) and 'armadura' (armor), which are part of the same word family.

English speakers can easily connect 'armar' to several similar English words like 'arm' (as in 'to arm someone'), 'arms' (weapons), 'armor', and 'armament'. All these words share the same Latin ancestry with the Spanish 'armar'. The military and defensive connotations have remained consistent across both languages throughout their evolution from Latin.